Optical modulator based on gamma -X valley mixing in GaAs-AlAs

Abstract

An optic modulator having a multiple quantum well structure which is fabrted of alternating layers of gallium arsenide and aluminum arsenide such that at zero electric field there is an indirect electron-hole transition between valence and conduction bands of the aluminum arsenide layers and gallium arsenide layers, respectively, and a direct electron-hole transition between the valence and conduction bands of the gallium arsenide wells. At zero field the multiple quantum well behaves much like bulk material due to the matching of the band gap energy levels of the gallium arsenide and aluminum arsenide. However, when a sufficient electric field is applied to the structure the energy levels decouple thereby modulating the wavelength of any light passing through the structure.

What is claimed is: 
     
       1. An optic modulator comprising: a multiple quantum well structure, the multiple quantum well structure comprising alternating layers of at least a first and second semiconductor material, the first and second semiconductor materials having predetermined band gap energy levels, compositions and thickcesses such that at zero electric field the θ state of the conduction band of the first semiconductor material is approximately equal to the x state of the second semiconductor material; and   means to apply an electric field to the multiple quantum well structure.   
     
     
       2. An optic modulator as in claim 1, wherein the first semiconductor material is gallium arsenide and the second semiconductor material is aluminum arsenide. 
     
     
       3. An optic modulator comprising: a substrate;   at least a first opaque ohmic contact applied on the substrate;   a multiple quantum well structure disposed on the substrate, the multiple quantum well structure comprising alternating layers of at least a first and second semiconductor material, the first and second semiconductor materials having predetermined band gap energy levels, compositions and thicknesses such that at zero electric field the θ state of the conduction band of the first semiconductor material is approximately equal to the x state of the second semiconductor material; and   at least a second opaque ohmic contact disposed on the multiple quantum well structure; and   a power source electrically connected to the first and second contacts.   
     
     
       4. The optic modulator as described in claim 3 wherein the first semiconductor is gallium arsenide and the second semiconductor is aluminum arsenide. 
     
     
       5. An optic modulator comprising: a substrate;   at least a first Schottky contact applied on the substrate;   a multiple quantum well structure disposed on the substrate, the multiple quantum well structure comprising alternating layers of at least a first and second semiconductor material, the first and second semiconductor materials having predetermined band gap energy levels, compositions and thicknesses such that at zero electric field the θ state of the conduction band of the first semiconductor material is approximately equal to the x state of the second semiconductor material; and   at least a second Schottky contact disposed on the multiple quantum well structure; and   a power source electrically connected to the first and second contacts.